Thermostat



Sept. 12, .1939.

c. G. KRONMILLER 2,172,820

THERMOSTAT H8 Hells 7 Filed Aug 28' 1936 H7 l'2;sSheecs-Sheei: l

f3' lo? J Sept 12, 1939- c G. KRONMILLER 2,172,820

THERMOSTAT Filed Aug. 28, 1936 3 Sheets-Sheet 2 I 171,1 94 20L 27 z3 5 E35 7 ao I lll al 5 4a 62 .e4/'17A j 39 8 8' 5y HAS' ATTORNEY Sept. 12,1939.

C. G. KRONMILLER 2,172,820

THERMOSTAT Filed Aug. 28, 1936 3 Sheets-Sheet 3 Patented Sept. 12, 1939UNITED STATES 'PATENT OFFICE THERMOSTAT Application August 28, 1936,Serial No. 98,326

26 Claims.

This invention relates to thermostats and more particularly to a type ofthermostatic appliance designed to be controlled by a timed mechanism.

One object of this invention is the provision of an improvedthermostatic appliance having in association therewith clockwork orsimilar mechanism designed to hold a thermostatic element bearing acontact in or out of engagement with an opposed stationary contact.

A further object of the invention is the provision of an improved meansfor setting a clock mechanism associated with a thermostat in suchmanner that the duration of the interval during which a contact carriedby the thermostatic element is held in or out of engagement with anopposed contact may be readily predetermined.

A further object is the provision of indicating means calibrated in sucha manner that the duration of the time during which the contacts areheld open or closed maybe readily determined at a glance. f

As conducive to a clearer understanding of the objects and purposes ofthis invention, it may here be pointed out that' in a heat controlsystem it 1s frequently desirable that the temperature value to whichetemperature controlling mechanism responds be lowered forapredetermined period, as for example, during the night or during suchperiods as the residents of the house, or other place where thethermostat may be located, are out. 0n such occasions it is advantageousto provide a simple mechanism whereby the temperature to which theheating plant responds may be lowered and subsequently raised againprior to the time of rising or reoccupancy of the dwelling. One subjectof this invention is to provide 'an improved mechanism whereby such achange may be readily accomplished and the duration of such changereadily determined in advance. As for example, if the resident leavesthe house for la period of five hours, he may set the thermostaticmechanism of the instant invention for a periodof, illustrative1y,.`four hours whereby during the first four hours-pf his absence the heatcontrolling mechanism responds to a temperature value of, i1-

lustratively, 60, but an hour before his return the temperature value towhich-the heating mech-- anism responds is raised to, illustratively,70,

yhereby the dwelling reaches this latter tempera- 1re before his return.Means to be hereinafter described are also provided whereby thetemperature values to which the device responds may be 'readily variedin accordance with the wishes of the operator.

(Cl. o- 139) The thermostatic mechanism to be hereinafter described maybe advantageously utilized in association with a second thermostat ofconventional design. A suitable method of associating the thermostat ofthe instant invention with a conventional room thermostat will behereinafter described in detail. When such a second thermostat isutilized, the arrangement is such that upon setting the mechanism of theinstant invention to operate for a predetermined period the saidmechanism serves to energize or deenergize the heat controlled mechanismat al predetermined desired temperature which may be anywhere within theeffective limits of adjustment of the instrument, as for example, theabove mentioned temperature of 60, At the termination of the operatingperiod the control of the heat controlled mechanism is returned ortransferred to the second or conventional room thermostatwhich may beset at any desired temperature as, illustratively, the abovementioned70.

Under certain circumstances as, illustratively, in warm climates it issometimes desirable that the heating mechanism associated with aresidence or other buildingbe .permitted to operate for only arelatively short period during each day and that at all times with theexception of this period it be dennitely precluded from operatingregardless of the temperature of the building.

In a modified form of the invention to be described hereinafter meansareprovided whereby upon setting the timed mechanism of the instantinvention, a burner or other heating mechanism is energized only for theperiod for which the timed mechanism is set provided the temperaturefalls below the predetermined point at which the instrument is set,means being provided whereby subsequent to the termination of such anoperating period the energimtion of the burner is positively precludeduntil such time as the mechanism is reset.

Other objects will in part be obvious and in part pointed outhereinafter.

The invention, accordingly, consists in the combination of parts,arrangements of elements and features of construction all as will bemore fully described hereinafter and shown in the accompanying drawingsand the scope of the application of which will be indicated 'by theappended claims.

In the drawings wherein are shown two illustrative embodiments of thisinvention:

Figure 1 is a side sectional elevational view lil 2 arrasa@ beingremoved;

Figure l is an enlarged sectional view of certain portions of themechanism as shown in Figure 1, certain other portions being' removedfor the sake of clarity;

Figure 5 is a perspective view of certain details of construction;

Figure 6 is an enlarged detailed View of certain portions of themechanism;

Figure 7 is a side sectional elevational view taken along line 1 1 ofFigure 6 as viewed from the right;

Figure 8 is a schematic view showing one form. of system with which themechanism of the nstant invention may be advantageously utilized;

Figure 9 'is a side sectional elevational view of a modified form ofstructure embodying the invention;

Figure 10 is a front elevational view of the structure shown in Figure9, certain parts thereof being removed for the sake of clarity;

Figure 11 is a view similar to Figure 10, certain parts thereof beingshown in a different position of adjustment and certain other partsthereof cut away;

Figure 12 is a view of a modified form of system with which thestructure shown in Figures 9'to 11, inclusive, may be advantageouslyutilized, and

Figure 13 is a fragmentary elevational view of a portion of a casingadapted to contain the operating ystructure of the instant invention.

Similar reference characters designate similar parts throughout theseveral views of the drawings.l

Referring now to the drawings, and more particularly to Figure 1, a baseplate 20 is secured to a wall W or other suitable place as by means Aofscrews 2l passed through suitable apertures in base plate 20. Secured tobase plate 20 as by screws 22 is a casing 23 adapted to contain aclockworks generally indicatedat 24l (see Figure 4), of any suitableform. In this connection, it may be pointed out that while any desiredclockworks may be utilized the form shown in the copending applicationof Andrew G. McNicholl, Serial No. 98,288, filed of even date herewithand assigned to the same assignee is eminently suitable for this use.Clockworks 24 will be referred to hereinafter in connection with certainelements thereof but for a more complete understanding of the structureandits mode of operation, reference is made to the above mentionedapplication of Andrew G. McNicholl.

As better shown in Figure 4, clockworks 24 includes a rear plate 25 anda front plate 26 secured in related assembly as by spacers 21 and screws28. A suitable main spring 29 mounted on a collet 34 secured to a shaft33 drives the clock mechanism through a gear train including a rst wheel30 and a second wheel 3| and others (not shown). A suitable slipfriction mechanism,

l generally vindicated at 4i, which is preferably of the ty'pe disclosedin the above referred to Mcliicoll application, is provided in orderthat main spring 29 may be tensioned or relievedof tension as desired ina. manner to be more fully described hereinafter. A gear 32 is splinedto shaft 35 and is adapted to mesh with a second gear carried by asleeve 86 and mounted for rotation on a pin 31 secured as by pee'ning tofront plate 26. Sleeve 36 carries a collar 38 having a projection 39thereon adapted under circumstances hereinafter described to abut aprojection 46 carried by the inner surface of casing 26.

A suitable starting mechanism which may advantageously be of the typedescribed in the above mentioned McNicoll application is also providedin order that when sleeve 36 is rotated to set the mechanism in a mannerto be described hereinafter, clockworks 24 may be started simultaneouslytherewith. Briey, the mechanism comprises a toothed pinion 50 mounted onan axle 5I which carries a collar 52 which in turn carries a pair ofspring arms 53 adapted to engage the balance wheel 54 of 4clockmechanism 24, a

spring 55 being positioned to abut pinion 50, all

pinion 50 past balance wheel 54 in order to impart initial impetusthereto to overcome any friction or inertia in component parts, theimpetus being continued by the tension of main spring 29.

Sleeve 36 has a flattened portion 56 at one portion of its peripherywhereon is mounted a collar 51 to which is rigidly secureda cam 58. Aset screw 59 passed through a suitable aperture in collar 51 precludeslinear movement thereof, llattened portidn56 preventing rotativemovement about sleeve 36. As better shown in Figure 3, cam 58 comprisesa substantially circular disk having 4a cut-away portion 60 havinginclined sides. A lug 6I is pivotally mounted as by a pivot 62 adjacentportion 60 and has an inwardly depending portion 63 engaging in a groove64 in cam 58 to limit the pivotal movement thereof.

Mounted about collar 51 is a resilient spring washer 69 which supports adial 10, means being provided as will be hereinafter described to holddial 18 inwardly against the pressure of disk 69.

. Dial 18 bears a series of suitable numerals on its n1l) engagedepending lugs 8| of a knob 82 having a knurled ridge 83 about itsperiphery. A relatively large aperture axially disposed through knob 82is adapted to receive a depending sleeve 84 of an operating handle 85,adapted to be mounted as by means of splines 86 for rotation with sleeve36. A screw 81 inserted through a suitable aperture in handle 85 andengaging with a threaded interior portion 88 (see Figure 5) of sleeve 36serves to hold the parts in related assembly.

From the foregoing, it will be seen that rotation of handle 85 rotatessleeve 36 through splines 86 and through gear 35 in turn rotates gear 32and shaft 33 to transmit motion to collet 34 and hence impart tension toor relieve tension `on spring 29 depending upon the direction oi.rotation of the handle 05. It will be understood ythat slip frictionmechanism 4| permits the s unwinding of spring 29 without aiectingclockworks 24 when handle 85 is rotated in a counterclockwise direction.It will also be seen that knob l2 may be rotated by means of knurledportion 83 independently of handle 55 and hence of sleeve \10 36 andthat such rotation, imparted through lugs and apertures 90 to dial 10,serves only to change the position of dial since it is freely rotatableabout collar 51. Moreover, it will be seen that rotation of handle 05also serves to vary the position oi cam 50 and its cut-away portion 90for a purpose to be more fully described hereinafter. The pressure oi!spring disk 69 against dial 10, however, forces collar 02 intoirictional engagement through a friction disk 39 g()d (see Figure 4)with the inner surface of operating handle 85 in such manner that whensleeve 30 is rotated by spring 29 through clockworks 24, handle 85 isrotated through splines 36 and such rotation is imparted through collar02 to dial 2o 1n.

It may here be pointed out that the instrunient is provided with -acasingl 90 secured by means of a screw 96 passed through a suitableaperture therein to base plate 2l. Casing 90 has,

30 at its upper and lower extremities, apertures 9-| to permit thecirculation of air about the-interior mechanism, the direction of suchcirculation being indicated by the arrows A (see Figures k 1 and 9). Anaperture 92 of a diameter to per- 35 mit the passage therethrough of asleeve 93 comprising an integral part oi' knob 32 is also provided incasing 90. Likewise, as best shown in Figure 13, an aperture 94 isprovided to permit certain of the numerals carried by dial 10 to be 40visible therethrough-from the exterior of casing 90. A pointer v95 iscentrally positioned with respect to aperture 94 and designates aspecific numeral or indication, the purpose of which will be describedhereinafter.

45 Referring back to Figures 1 and 2 a bimetallic element |00. one endof which is secured in an insulating block |0| as by screws |02 passedthrough suitable insulating washers (not shown) is mounted on adepending arm |04- forming a 50 part of a member |05 which is mounted asby means of a U-shaped bracket |05 on a post |01 for pivotal movementthereabout. A spring clip |00 .serves to hold bracket |05 in relatedassembly with post |01. A coil spring |09 positioned 55 about post |09has one end hooked behind mem-n ber |05 as shown at l0. The other end ofspring |09 abuts a post having a reduced end on which a sleeve ||2 ismounted for, rotation. The arrangement is such that member |05 is biasedby oo spring |09 in such a manner that it tends to rotate in a clockwisedirection (as seen in Figure 2) about post |01 for a purpose to be laterAs better shown in Figure 1, post has rigidly mounted-thereon a springclip ||3 o5 which has' a `form comprised of a 'plurality' ofresilient-1y extending arms one oi which, ||5. is

bent forwardly to form a pointerrJI'he otherv arms of spring clip ||3serve to holdresiliently 'an indicating dial ||9 mounted on sleeve ||270 'against a spring clip Dial ||3 has a groove ||l thereinthroughwhichpointer ||5 passes in such a manner as to be visible from the front o1lthe device. The indicia carried by dial ||91may take a form' tocorrespond to the degrees of tem- 'ju perature at which 1t is desired toset the meenanism. A suitable aperture ||9 in casing `90 permits thepassage therethrough of the uppermost portions of dial I9 and pointer |5whereby they are visible from the exterior of casing 90. A cam lisrigidly secured to sleeve ||2 and adapted to abut an adjustable screwcarried by an extending portion |29 of member |05.

Thus, it `will be seen that spring |09 serves to force member |05 andscrew |30, carries there' by, normally into abutting relation with cam|20 and that such force acting through member |04 serves to hold the endof bimetallic element |00 opposite insulating block |0| in a givenposition. As dial ||5 is rotated, cam |20 is rotated therewith and asits high portion abuts screw |30 and end of bimetallic element |00opposite insulating block |0| is forced in one direction against thepressure of springV |09 and, correspondingly, as the low-portion of cam|20 abuts screw |30 the said'end of bimetallic element |00 is forced inthe opposite direction by spring |09, screw |30 likewise being held inabutting relation with cam |20 thereby. Screw |30 may be readilyadjusted by rotation to vary the position of member |05 for any givenposition of cam |20 in order to provide accurate calibration oi theinstrument in a manner to be hereinafter described.

As better shown in Figure 6, a spring leaf member |32 is secured as by arivet |33 to the rear..iace oi bimetallic element |00. A contact |3| issecured to member |32 and passed through a suitable aperture in element|00. A metallic arm |34 is also secured as by a rivet |20 to bimetallicelement |00 in a position adjacent contact |3,|. vOpposed to contact |3|is a contact screw |35 mounted in a suitable bracket |36 secured to aninsulating block |31 carried by panel 20. A terminal screw |38 inelectrical contact with bracket |36 and hence contact screw |35 engages.one end of a lead wire |39. A second lead wire .|40 leads to a secondterminal `screw |4| from which a wire |42 leads through insulating block|0| to electrical contact with the end of bimetallic element |00 securedthereto. A magnet |43 is supported vin a suitable bracket |44 and heldby a screw |45 in a position adjacent arm |34 to impart a relative snapaction to the movement oi' bimetallic element |00 and hence to contact|3| in a well known manner. Thus, it will be seen that as contact |3|engages contact screw |35, a circuit comprising, in the instrument, wire|40, terminal |4|, wire |42, bimetallic element |00, spring leaf member|32, contact |3|, contact screw |35, member |36, terminal |30'and wire|39, is closed.

The parts hereinbefore described with one exception to be hereinafterdescribed have been common to both modications of the device as shown inthe accompanying drawings. Now, however, having particular reference tothe modiiication shown in Figuresl l to 7, inclusive, a

y bell-crank member is mounted on a pivot |5| and has an extendingprojection |52 adapted to abut the surface of cam 58, such abutmentbeing assured by the action of a vcoil spring |53 positioned about post|5|. 'I'he opposite end of bell-crank lever |50 has an upwardly turnedportion |54 which has secured thereto, as better shown in Figure 5, aU-shaped insulating block |53, the legs of the U being spaced apart adistance slightly greater than the width of bimetallic element |00.Insulating block |55 thus serves positively to hold contact |3`| inengagement with contact |35 regardless oi temperature fluctuationsv atall times during the inoperative period of the device or when projection|52is juxtaposed to cut away portion B0. yThe legs of Ueshapedinsulating member |56 are spaced from the sides of bimetallic element adistance less than the diameter of contact |3| and serve to preclude,lateral displacement thereof with respect to contact screw |35 throughaccidental jars such as might occur in shipping or mounting theinstrument.

From the foregoing, the operation of the device should now be apparent.Dial |6 is'frst rotated until a numeral indicative of the desiredtemperature to which the device will respond is adjacent pointer H5.Dial 10 is then rotated by means of knurled portion 83 of knob 82 untila number corresponding to the instant time of day is visible throughaperture 94 adjacent pointer 95. Knob 85 is then rotated, such rotationbeing imparted to cam 58- through sleeve V51 and likewise throughspring` clip 69 to dial 10. When a number indicative of the time of dayat which it is desired that the operation of the mechanism bediscontinued is juxtaposed to pointer 95, rotation of handle 85 isdiscontinued and the position of cut-away portion 60 is such that itwill rotate to a position adjacent projection |52 in a periodcorresponding to the number of hours betweenthe time of day and thenumber opposite pointer 95 at the termination of the setting operation.The cam action of cam 58 against projection |52 moves lever |50 andhence insulating block |56 away from bimetallic element |00 which is nowfree to move in the manner above mentioned in response to temperaturevariations to engage contact |35 or to separate therefrom in accordancewith the temperature conditions' in the adjacent space as exemplified bythe flow of air passing through apertures 9|. It will correspondingly beseen that rotation of handle 85 imparts tension to main spring 29 in themanner above described, and through rotation of gear 35 and the startingmechanism previously described simultaneously starts clockworks 2li. Thetension imparted to spring 29 is gradually relaxed through theclockworks 24 which now rotates sleeve 35 and dial 58 in acounter-clockwise direction. Segment 5| rotates 1 about its pivot 52 dueto the force of gravity, partially covers cut-away portion 50 and increases the peripheral extent of the high portion of cam 58. Y

Segment 5| thus provides a means whereby y contact |3| mayengage contactscrew |35 in a relatively rapid manner or with a snap action. It will beseen that upon manual rotation of handle 85, segmentvi may rotate aboutits pivot 62 in accordance with the pressure of projection |52 thereonin such manner that projection |52 rides gradually up the inclinebetween the low portion and the high portion. However, upon reverserotation of cam 58, segment 5| rotates as above described until itcompletely covers the incline between the high portion and the lowportion of cam 58, thus providing a relatively sharp angle between thehighY portion and the low portionV thereof'.y Accordingly, when cam 58has rotated until projection |52 is adjacent the above mentionedextremity of segment 8|, spring |53 will force projection |52 inwardlyinto juxtaposition with the low portion of cam 58 with an abruptmovement since the angle of travel is substantially a right or an acuteangle with respect to a tangential line taken at a point coincident withthe junction of the high portion with the incline .leading thereto.Furthermore, it is essential that.4

arrasa@ the cut-away portion 58 should be oi a relatively small extentin order lto provide a maximum time of operation :tor the instrument,and were pivoted segment 5| not provided, the angle of the aperture upwhich projection |52 is forced to ride would be so steep as to occasionthe possibility of sticking or binding in the mechanism. A greaterangle, as above pointed out, would provide not only a larger apertureand a consequent lesser period of operation but would also obviate theadvantages achieved by the relative snap action imparted to contact I 3|in the manner above described.

` It may here be pointed out that cut-away portion 60 is in substantialalignment with projection 39 and likewise that projection |52 is insubhandle 85 and its relative position with respect to pointer 95indicates not only the position of cutaway portion 60 but likewise ofstop 39. After the clock mechanism has' rotated cam 58 as abovedescribed until projection |52 has entered cutaway portion 60, theclockworks will run for a relatively short period, `preferablysufficient only to insure continued rotation until such time as thecontacts |3| and |35 have been closed in the manner above describedwhereupon the abutment of stop 39 with stop 40 will cause the operationof clockworks 24 to be discontinued.

It should here be pointed out that should it be desired to discontinuethe operation of the mechanism at any time prior to the time for whichthe device is set, counter-clockwise rotation of han dle 85 as seen inFigure 2, which is permitted by slip friction mechanism 4|, will resultin the immediate engagement oi projection |52 with cutaway portion 50and a consequent positive closure v,of contacts |3| and |35.

`Referring now to Figure 8, wire |39 is disclosed as leading fromcontact |35 through the secondary |65 of a step-down transformer,generally indicated at |5|, which includes a primary |62 connectedthrough wires |63 and |64 to line wires |55 and |86, respectively. Fromsecondary |50 a wire |81 leads through a relay coil |68 to a junction|89 and thence through a wire |10 to a contact opposed to a contact |12carried by a bimetallc room thermostat of standard design, generallyindicated at |13. Thermostat |13 has a second contact |14 which isadapted to engage an opposed contact |15 to which wire |40 leads.Contacts |1||12 engage at a slightly lower temperature than contacts|14|15 in order to provide a slight operating differential in a wellknown manner. From the terminal |15 of thermostat |13, a wire I 11 leadsto a contact |18 cooperable with a relay switch arm |19 from which awire leads to junction |69. From line wire |56, a wire |8| leadsdirectly to a contact |82 which cooperates with a second relay switcharm |83 from which a wire |84 leads to a Stoker motor |85 or `otheranalogous heat control mechanism. From stoker motor |85 a wire |86 leadsto line wire |65. Thus it will be seen that in the system shown,contacts |3| and |35 are normally engaged when the mechanism hereindescribed is not operating. Thermostat |13 is set for operation in aconventional manner and as contact |15 engages contact |15 and upon afurther drop in temperature contact |12 engages Contact |1|,

an energizing circuit is established, comprsedof 15 transformersecondary |60, wire |61, relay coil |68, junction |69, wire |10,contacts |1| and |12, |14 and |15, wire |40, terminal |4|, wire |42,bimetallic member |00, contacts |3| and |35, wire |39 back totransformer secondary |60. Such energization of relay coil |66 pulls inrelay switch arms |19 and |83 whereupon the engagement of arm |19 withcontact |18 establishes a holding circuit comprised of transformersecondary |60, wire |61, relay coil |68, junction |89, wird |80, arm|19, contact |18, wire |11, terminal |16, thermostat |13 contacts |14and |15, wire |40, terminal |4|, wire |42, bimetallic element |00,contacts |3| and |35, wire |39 back to transformer |60. It `may here bepointed out that upon a drop in temperature suflicient to separatecontacts |1| and |12 the above described holding circuit is not brokenand relay coil |68 is thus maintained energized until a continued dropin temperature' causes contacts |14 and |15 to separate.Correspondingly, with the engagement of arm |83 with contact |82 acircuit through stoker motor |85 is also established, as will be readilyapparent, however, when the mechanism is set in the manner hereinbeforedescribed, bimetallic element is free to move contact |3| away fromcontact |35. Consequently, when contacts |1| and |12 and |14 and |15engage at a temperature of, illustratively, 70, and 72- respectively, nocircuit will be established since contacts |3| and |35 will remain openuntil the temperature has fallen to that to which the instrument of theinstant invention is set. In Figure 2 for example, the mechanism is setat 55. Assume this to be the case with the thermostatic mechanism shownin Figure 8. When the temperature has fallen to 55, contact |3| engagescontact |35 and the circuits previously described are completed.However, immediately upon a rise in temperature above 55,illustratively, contacts |3| and |35 separate to break any circuitsextending through relay coil |68 since it will be readily apparent thatall circuits, energizing or maintaining, through relay coil |68 mustpass through contacts |3| and |35. However, upon the termination of thetimed period of operation when cam 58 has rotated to its off position,the engagement of projection |52 and cut-away portion 60 will permitspring |53 to move insulating block |56 and hence bimetallic element |00and contact |3| inwardly with asnap action occasioned by segment 6| asabove described into engagement with contact |35, whereupon stoker motor|85 will remain energized through the circuits previously describeduntil the temperature has risen to illustratively '12 to break contacts|14 and |15 and thereafter operation of the device will becontrolled'through thermostat |13 until 4 the mechanism of the instantinvention is again manually set in operation.

Referring now to the modification shown in Figures 9, l0 and 11, thereis substituted for the lever |50 a lever |90 which has an inturnedprojection |9|, corresponding to projection |52 of lever |50, adaptedunder certain circumstances to engage with cut-away portion 60 of cam58. Lever |90 has a downwardly depending portion |92 covered withinsulating material |93 and positioned between the extending members ofmagnet |43, the arrangement being such that as a high portion of cam 58abuts inwardly turned projection |9|, insulation |93 surroundingdownwardly depending portion |92 forces bimetallic element |00 and itscontact |3| out of engagement with contact screw |35 and holds the samein such position regardless of temperature variations.

In this modication additional means are also provided whereby contact|3| may be continuously held from engagement with contact |35 regardlessoi' the position of the timing mechanism and the consequent position ofcam 58. Such means take the form of a lever |94 having an aperture |95therein adapted to encircle sleeve. 36. Projections |96 and |91 struckupwardly from lever |94 are adapted normally to clear cam 58 but toprevent slippage of lever |94 in a diicction towards the ri-ght asviewed in Figure 9. Likewise, when lever 94 is forced downwardly in amanner to be described hereinafter, projection |91 is designed to abutprojection |9| of lever |90 in such manner as to force the samedownwardly and hence insulating member |93 outwardly against thepressure of a spring |98 which corresponds to spring |53. The upper endof lever |94 is provided with-a forked portion comprised of legs |99 and200 adapted to pass on opposite sides of `sleeve IIZ, corresponding tosleeve ||2. Leg 200 has formed thereon an upstanding lug which isadapted under certain circumstances to be engaged by a projection 202carried by sleeve ||2'. In a dial ||6 corresponding to dial ||6, thelowermost temperature setting is replaced by an indication oi. Thearrangement is such that when the indication oil is adjacent pointer||5, projection 202 abuts projection 20| and consequently forces lever|94 downwardly, such movement as above stated being imparted throughupstanding portion |91 to projection |9|` and hence through lever |90and its insulated portion |93 to bimetallic element |00 whereby contacts|3| and |35 are held separated until dial ||6 is rotated out of its ofil portion to a position indicative'of the fact that bimetallic element|00 is free to respond to temperature variations except as restricted bythe operation of the timed mechanism.

As previously stated the structure shown in the modincationLimmediately-above described is designed for use in comparatively mildclimates and may be advantageously utilized alone as controlling meansfor a burner obviating the necessity for a second thermostat asdescribed in the previous specification. When desired, the owner may setthe time mechanism for a period of from one to substantially twelvehours in accordance with the length of time he wishes the burner to bedenitely inoperative, which period may correspond to the length of timehe expects to be absent from home or the duration of the period fromretiring to an hour just prior to arising, whereby the dwelling or'other place may be adequately heated upon his return or in the morning.During the time the instrument describedimmediately above is set,contacts |35 and |3| will be unable to engage and, accordingly, no heatcan be generated while the instrument is in operation. Similarly, inparticularly warm weather by simply turning dial ||6 to its off positionthe operation of the heating mechanism may be completely discontinueduntil such time as the instrument is reset. In Figure 12 there isdisclosed a system wherein the structure shown in Figures 9 to 11 may beadvantageously used. A conventional step-down transformer, generallyindicated at 2|0, is comprised of a primary 2|| and a secondary 2|2 andsupplied with power from any suitable source `(not shown). Wire |40leads from secondary 2|2 to terminal |4| from which, as in connectionwith the system disclosed in Figure 8, wire |42 leads to bimetallicelement |00. Contact |3| carried by bimetallic element ventional mercuryswitch MS.

Il mi is" positioned opposite contact screw G35 from which wire iti@leads to one `terminal of a con- Mercury switch 2id comprises a portionof a conventionaly high limit control, generally indicated at 2M, andincludes operating mechanism 2lb actuated in a known manner by avolatile duid illled bellows 2l@ in association with a controlling bulb2M associated with the heating plant in a well known manner. A spring225 serves to hold switch 2 i3 in circuit closing position in theabsence of pressure imparted to mechanism 2W by bellows 2 i6. From theother terminal of mercury switch M3, a wire 269 leads to one end of acoil 22|! surrounding a plunger 22E which operates a valve 222positioned in a full supply line 2123 leading to a burner `2|8. From theother end of coil 22d a wire 224 leads back to transformer secondary2|2. Thus it will be seen that ,when contacts l3| and |35 are separated,valve 222 is closed. Valve 222 remains closed until such time as anenergizing circuit, readily discernible from a consideration of Figure12, is provided by closure of contacts |3| and |35. This circuit retainsvalve 222 open to provide fuel to burner |28 until such time as contacts43| and |35 separate provided, of course, that during the interim thetemperature in the heating system does not rise sufficiently to causeexpansion of bellows 2|6 to tilt mercury switch 2|3 to circuit openingposition. As above pointed out, contacts |3| and |35 may be held openeither by means of the lever |94 or through the operation of the timermechanism above described.

From the foregoing, it will now appear that there is thus provided animproved structure accomplishing the objects of the invention and othersincluding many advantages of great practical utility.

As many modifications may be made in the inventive concept hereindisclosed and as many changes may be made in the illustrative embodimentshown,'it is to be understood -that all matter hereinbefore described ordisclosed in the accompanying drawings is to be interpreted asillustrative and not in a limiting sense.

I claim as my invention:

1. In a device of the character described, in'Y combination, a conditionresponsive element, one

end thereof being movable in accordance with- .condition change, contactmeans carried by the movable end of said element, second contact meansin the path of movement of said first contact means, a timed operatingmechanism, al

shaft rotated by said mechanism, a cam carried by said shaft, a levermovable by said cam and positioned iri the path of movement of saidelement, means associated with said shaft to predetermine the operatingperiod of said mechanism, said means also positioning said cam with.respect to said lever, and means associated with said lever positivelyto hold said element and hence said first contact means adjacent one ofits limits of movement.

2. In a device of the character described, in combination, a conditionresponsive element, one end thereof being movable in accordance withcondition change, contact means carried by the movable end of saidelement, second contact means in the path of movement of said firstcontact means, a timed operating mechanism, a shaft rotated by saidmechanism, a, cam carried by said shaft, a lever movable by said cam andpositioned in the path of movement of said element, means associatedwith said shaft to prearmeno determine the operating period of saidmechanism, said means also positioning said cam with respect to saidlever, and means associated with said lever positively to hold saidelement and hence said rst contact means in engagement with said secondmentioned contact means-except during the operating period of said timedmechanism.

3. In a device of the character described, in combination, a conditionresponsive element, one end thereof being movable in accordance withcondition change, contact means carried by the movable end of saidelement, second contact means in the path of movement of said iirstcontact means, a timed operating mechanism, a shaft rotated by saidmechanism, a cam carried by said shaft, a lever movable by said cam andpositioned in the path of movement of said element, means associatedwith said shaft to predetermine the operating period of said mechanism,said means also positioning said cam with respect to said lever, andmeans associated`with said lever positively to hold said element andhence said first contact means out of engagement with said secondcontact means during the .operating period of said timed mechanism.

4. In a device of the character described, in combination, a timedoperating mechanism, cam means rotatable by said timed operatingmechanism, a lever movable by said cam means, a temperature responsiveelement adjacent said lever, a contact carried by said temperatureresponsive element, a fixed contact adjacent said first mentionedcontact, said element causing opening and closing of said contacts upontemperature changes and means associated with said lever to hold saidAfirst and second contacts out of engagement regardless of temperatureconditions during the operating period of said timed mechanism. v

5. In a device of the character described, in combination, a conditionresponsive element, a contact carried by said element, a second contactadapted to engage said first mentioned contact, a timed operatingmechanism, a cam rotatable by said mechanism, a lever movable by saidcam carried by said lever, means to adjust the position of saidcondition responsive element whereby said rst and second contacts engageand disengage at various condition values, and means to preclude theengagement of said contacts regardless of said condition value.

6. In a device of the character described, in combination, a bimetallicelement, a timed operating mechanism, a cam rotatable by said timedoperating mechanism, a lever adjacent saidicam, spring means to hold oneend of said lever adjacent said cam, the other end of said lever beingpositioned adjacent said bimetallic element', a contact carried by saidbimetallic element, and a second contact adjacent said rst mentionedContact, the arrangement being such that when said lever engages alow-portion of said cam said contacts are held in engagement by abutmentof said lever with said bimetallic element but when said lever abuts ahigh-portion of said cam said contacts may open or close in response totemperature conditions.

7. In a device of the character described, in combiration, a timedoperating mechanism, a bimetallic element, a cam rotatable by said timedoperating mechanism, a lever adjacent said cam and said bimetallicelement, a contact carried by said element and a second contact adjacentsaid rst mentioned contact, the arrangement engage when said timedoperating mechanism is in operation.

8. In a device of the character described, in combination, a timedoperating mechanism, a

bimetaliic element, a cam rotatable by said timedl operating mechanism,a lever adjacent said cam and said bimetallic element, a contact carriedby said element and a second contact adjacent said iirst mentionedcontact, the arrangement being such that when said timed operatingmechanism is in operation said contacts may separate or engage inIresponse to temperature changes and when said timed operating mechanismis not in operation said lever holds said contacts in engagement, andmeans to vary the temperature value at which said contacts will separateor engage .when said timed operating mechanism is in operation, saidlast mentioned means comprising a rotatable cam and a member juxtaposedto said cam and associated with an end of said bimetaliic elementwhereby rotation of said cam Varies the position of said end of saidbirnetallic element,

, and hence the relative distance between said contacts at a giventemperature value.

9. In a device oi' the character described in combination, a conditionresponsive element, a

f contact carried therebya second contact adjacent said iirst mentionedcontact, means to vary the relative position of said first contact withrespect to said second contact whereby -said contacts will engage atvarying condition values, a clock mechanism, a cam rotatable by saidclock mechanism, a pivoted lever adjacent said cam and movable therebyand means associated with said lever to restrict the movement of saidcondition responsive element and. hence said contact carried thereby inaccordance with the position of said cam regardless of said conditionvalue.

10. In a device of the character described in combination, a conditionresponsive-element, a

contact carried thereby, a second contact adjacent said first mentionedcontact, means to vary lthe relative position of said second contactwith respect to said first contact whereby said contacts ywill engage atvarying condition values, said means comprising a rotatable cam and alever associated with an end of said condition responsive elementwherebyrotation of Ysaid cam moves said lever to vary the position ofsaid condition responsive element and hence said contact carriedthereby, a clock mechanism, a second cam rotatable by said clockmechanism, a pivoted lever' adjacent said second cam and movable therebyand means associated with said pivoted lever to restrict the-movementofsaid contact carried by said condition responsive element in accordancewith the position of said second cam regardless of said condition value.

1l. In a device oi' the character described in combination, a conditionresponsive element, a. contact carried thereby, a second contactadjacent said first mentioned contact, a clock mechanism, a sleeverotatable by said clock mechanism, a dial carried by said sleeve,indicia on saidfdial, a fixed pointer adjacent a peripheral portion ofsaid dial, a cam carried by said sleeve, a lever pivoted adjacent saidcam and movable the movement of said condition responsive eleaccordancewith the position ofsaid cam regardless of condition values, thearrangement being such that the position of the indicia carried' by saiddial with respect to said pointer indicates the relative position ofsaid cam in respect to said lever.

12. In a device of the character described in combination, a conditionresponsive element, a contact carried thereby, a second contact adiacentsaid first mentioned contact, means to vary the relative position ofsaid second contact with respect to said iirst contact whereby saidconiacts will engage at varying condition values, a clock mechanism, asleeve rotatable by said clock mechanism, a dial carried by said sleeve,indicia on said dial, axed pointer adjacent a peripheral portion of saiddial, a cam carried by said sleeve, a lever pivoted adjacent said camand movable thereby, member carried by said lever to restrict themovement of said condition responsive element and hence said contactcarried thereby in accordance with the position of said cam regardlessof condition values, the arrangement being such that the position of theindicia carried by said dial with respect to said pointer indicates therelative position of said cam in respect to said lever.

13. In a device of the character described in combination, a conditionresponsive element, a contact carried thereby, a second contact adjacentsaid first mentioned contact, a cam, a lever adjacent said camassociated with said condition responsive element, the arrangement beingsuch m,

4clock mechanism, a second cam rotatable by said clock mechanism, anindicating dial rotatable with said cam, a second lever adjacent saidsecond cam and movable thereby and means associated with said secondlever to restrict the movement of said condition responsive element andhence said contact carried thereby in accordance with the position ofsaid cam regardless of said condition value, the arrangement being suchthat the relative position of said indicating dial indicates therelative position of said second cam with respect to said second lever.

14. In a device of the character described in combination, a conditionresponsive element, a contact carried thereby, a second contact adjacentsaid rst mentioned contact', atimed opeating mechanism, a cam rotatableby said timed operating mechanism, a lever adjacent said cam and movablethereby, spring means to hold said lever adjacent said cam, insulatingmeans associated with said lever to restrict the movement of saidcondition responsive element and hence said contact carried thereby inaccordance with the position of said cam regardless of said conditionvalue and means to indicate the relative position of said cam withrespect to said thereby, member carried by said lever to restrict lever.

15. In a device of the character described in combination, a conditionresponsive element, a

contact carried thereby, a second contact adjacent said first mentionedcontact, a timed operating mechanism, a cam rotatable .by said timedoperating mechanism, a lever adjacent said cam and movable thereby,spring means to hold said lever adjacent said cam, insulating meansassociated with said lever to restrict the movement of said conditionresponsive element and hence said contact carried thereby in accordancewith the position of said cam regardless of said condition value andmeans to indicate the relative position of said cam with respect to saidlever, said last mentioned means comprising a dial having time denotingnumerals thereon and a pointer, said dial being rotatable with said camwhen said cam is rotated by said timed operating mechanism but manuallyrevolvable independently of said cam and said timed operating mechanismWhereby said time denoting numerals may be utilized to indicate theAduration of the operating period. of the mechanism.

\16. A device of the character described, comprising in combination, acondition responsive element, a contact carried thereby, a secondcontact carried adjacent said first mentioned contact, a timedmechanism, a cam rotatable by said timed mechanism, a lever adjacentsaid cam and movable thereby, means carried by said lever to restrictthe movement of said condition responsive element and hence said contactcarried thereby in accordance with the position of said cam regardlessof the value of said condition and means carried by said cam to imparta. snap action to the movement of said lever.

17. A device of the character described, comprising in combination, acondition responsive element, a contact carried thereby, a secondcontact carried adjacent said rst mentioned contact, means to vary therelative position of said rst mentioned contact with respect to said second mentioned contact whereby said contact will engage at variedcondition values, a timed mechanisrn, a cam rotatable by said timedmechanism, a lever adjacent said cam and movable thereby means carriedby said lever to restrict the movement or said condition element andhence said contact carried thereby in accordance with the position oisaid cam regardless of the value oi said condition and means carried bysaid' cam to impart a snap action to the movement or said lever.

18. ln a device of the character described, comprising in combination, acondition respon= sive element, a contact carried thereby, a secondcontact carried adjacent said hrst mentioned contact, a timed mechanism,a cam rotatable by said timed mechanism, a lever adjacent said cam andmovable thereby, means carried by said lever to restrict the movement oisaid condition element and hence said contact carried thereby inaccordance with the position oi said cam regardless of the value of saidcondition, and means associated with said cam to impart a snap action tothe movement of said lever, said means including a spring associatedwith said lever.

19. In a device of the character described, comprising in combination, acondition responsive element, a contact carried. thereby, a secondcontact adjacent said rst mentioned contact, a timed mechanism, a'camrotatable by said timed mechanism, said cam .having a high portion and`a low portion, a lever adjacent said cam and movable thereby, meansassociated with said lever to restrict the movement of said conditionresponsive element and hence said contact carried thereby in accordancewith the position of said cam and means carried by said cam to impart asnap action to the movement of said lever, said means comprising aninclined surface on said cam comprising a substantially right angle, andresilient means associated with said lever whereby upon juxtaposition ofsaid right angle surface arrasa@ or' said cam to said lever, saidresilient means iorces said lever abruptly from said high portion tosaid low portion.

20. lin a. device of the character described, comprising in combination,a condition responsivev element, a contact carried thereby, a secondcontact carried adjacent said first mentioned contact, a timedmechanism, a cam rotatable by said timed mechanism, said cam having ahigh portion and a low portion, a lever adjacent said cam and movablethereby, means carried by said lever to restrict the movement of saidcondition responsive element and hence said contact carried thereby inaccordance with the position of said cam regardless of said conditionvalue, and means carried by said cam to impart a snap action to themovement oi' said lever, said means including a pivoted segment carriedby said cam and constituting an extension of the high portion of saidcam.

21. In a device of the character described, comprising in combination, acondition responsive element, a contact carried thereby, a secondcontact adjacent said first mentioned contact, a timed mechanism, a camrotatable by said timed mechanism, said cam having a high portion and alow portion and an incline therebetween, a lever adjacent said cam andmovable by rotation thereof, said lever serving to restrict the movementof said condition responsive element and hence said contact carriedthereby in accordance with the position of said cam regardless of saidcondition value, and means associated with said cam to impart a snapaction to the movement of said lever, said means comprising a pivotedsegment carried by said cani adjacent said incline, and resilient meansassociated with said lever the arrangement being such that upon rotationof said cam in one direction said lever rides upsaid incline but uponreverse rotation of said cam said pivoted segment moves into the path cisaid lever whereby the angle of said incline is varied and said lever'upon reaching,r the extremity of said pivoted segment moves to the lowportion of said cam with an abrupt movements 22. In a device of thecharacter described in combination, a member to be moved in response totemperature variation, a mechanism controlled thereby, a second memberto restrict the movement oi' said drst mentioned membena timed operatingmechanism to control the position of said second member, means to varythe temperal ture value to which said first member responds, and' meansassociated with said last mentioned means to actuate said second memberto rst member controlling position independent of said timed operatingmechanism.

23. In a device of the character described in combination, a member tobe moved in response to temperature variation, a mechanism controlledthereby, a second member to restrict the movement of said rst mentionedmember, a timed operating mechanism to control the position of saidsecond member, means to vary the temperaturevalue' to which said firstmember responds, and means independent of said timed'operating mechanismto restrict movement of said rst mentioned member regardless oftemperature conditions.

24. A device of the class described, comprising in combination, a membermovable back and forth, said member having a cut-away portion which isconnected to the other portion of said movable member by a gradualsloping inclined portion, c. controlled member biased to engage ,ivasao'-'pivoted on said movable member and arranged to overlie said gradualsloping inclined portion whereby upon movement of said movable member inone direction said controlled member abruptly y moves from the end otsaid pivoted member to the lower-most part oi' said cut-away portion.

25. In a device of the character described. in combination, a conditionresponsive element, a switch operable to both open and clod positions bysaid element, a timed operating mechanism, a

manually operable setting means for said mechanism, and moanscooperating with'said mechanism for positively holding said switch inone of its positions for a length of time dependent upon the setting ofsaid mechanism.

26. In a device of the character described, in combination, a conditionresponsive element, a mechanism operable to both of two controllingpositions thereby, a timed operating mechanism, a manually operablesetting means for said mechanism, and means cooperating with said timedoperating mechanism for positively holding said ilrst mentionedmechanism in one of its 'controlling positions for a length of timedependof said m.

